Brighton_Earthship_entrance - Passive solar/greenhouse Facade that could perhaps be added to an ordinary home. (Don't like the funky angles, but this is the beginning of the right idea.

fireplace surrounded by sculpted cob - a mixture of clay, sand & straw - that absorbs the heat from the fire and stays warm long after the fire is done burning. Much more efficient than a regular fireplace (which can have a net cooling effect).